Pentacene on graphene: Differences between single layer and bilayer

Using atomic force microscopy we have examined morphology of sub-monolayer thick pentacene layers, deposited on exfoliated single-layer and bilayer graphene, transferred onto SiO2. We observe two-dimensional island growth in the range of substrate temperatures from 10 to 60 °C. We find that island size distributions on single-layer graphene are broader and centered at higher average island areas than on bilayer graphene. We have found activation energy for molecule aggregation of Ea = 427 ± 25 and Ea = 537 ± 46 meV for single layer and bilayer graphene, respectively. We associate the observed differences in pentacene layer morphology with the influence of the dipole field that can be associated with the water layer at the graphene/SiO2 interface.